African, European Kids Have Different Gut Bugs

Action Points

Point out to interested patients that the human intestine contains trillions of organisms which contribute to our ability to metabolize food and resist certain infections.

Explain that this study suggests that the composition of the bacterial flora is determined at least in part by diet and environmental factors in different cultures.

Children on a Western-style diet appear have different gut bacteria compared with African children, whose eating habits and living environment more closely resemble those of earlier ancestors, researchers have found.

The researchers compared fecal microbiota from 14 healthy young African children living in a rural village in Burkina Faso with that of 15 age-matched Italian children from urban Florence -- and although the four most common bacterial phyla were found, the amount of each differed between the two groups, according to Paolo Lionetti, MD, of the University of Florence, and colleagues.

For example the African kids had more Actinobacteria and Bacteroidetes while the Italians had more Firmicutes and Proteobacteria -- a difference that could play a role in future health problems, Lionetti and co-authors reported in the Proceedings of the National Academy of Sciences.

In particular, the increased ratio of Firmicutes to Bacteroidetes might predispose children eating typical Western diets to future obesity, the researchers wrote.

The African children also had two types of bacteria totally absent in the Italian kids -- Prevotella and Xylanibacter -- that produce more short-chain fatty acids, known to be protective against inflammation.

The findings could partially account for an increased prevalence of obesity, allergy, and autoimmune diseases that are largely absent in rural African populations, Lionetti told MedPage Today, although more research needs to be done.

"We know that in developed countries there's a high incidence of obesity, allergy, autoimmune disease, and irritable bowel syndrome, even in children now," Lionetti said. "Children in the developing world don't get those diseases, although they do have problems like malnutrition and infection."

The human gut contains trillions of microbes that contain at least 100 times as many genes as the human genome alone. This vast microbe colony provides enhanced metabolic capabilities and protection against pathogens.

But researchers don't know how different living environments and the varied diets around the world have affected the microbial ecology of the human gut.

So Lionetti and colleagues compared the fecal microbiota of 15 children ages 1 to 6 from urban Florence with that of 14 African children of the same age living in the small rural village of Boulpon -- a living environment that still resembles that of humans during the agricultural revolution about 10,000 years ago.

The daily diet in the African village is high in fiber, starch, and plant polysaccharides and low in fat and animal protein -- consisting mainly of cereals, legumes, and vegetables.

The researchers found significant differences in gut microbiota between the two groups. All of the children were found to have the four most common intestinal bacterial phyla -- Actinobacteria,Bacteroidetes, Firmicutes, and Proteobacteria.

But the African children had more Actinobacteria and Bacteroidetes, while the Italian kids had more Firmicutes and Proteobacteria:

Italian children: 10.1%, 6.7%, 63.7%, and 27.3%, respectively

African children: 57.7%, 22.4%, 6.7%, and 0.8%, respectively

The increased Firmicutes to Bacteroidetes ratio was likely the result of higher fiber intake among the Africans, maximizing metabolic energy extraction from ingested plant polysaccharides, the researchers suggested.

"Reduction in microbial richness is possibly one of the undesirable effects of globalization and of eating generic, nutrient-rich, uncontaminated foods," they wrote.

African children also had bacteria from the genus Prevotella and Xylanibacter -- known to contain a set of bacterial genes that can ferment cellulose and xylan -- that were completely lacking in the European children.

These bacteria produce more short-chain fatty acids, Lionetti said, which have been proven to protect against gut inflammation. As expected, the researchers saw significantly more short-chain fatty acids in African children (P<0.001).

There were also clear variations in total calorie content between the two groups, ranging from about 670 calories for the youngest group to 1,000 calories for the oldest African groups, while the youngest Italians consumed 1,070 calories and the oldest, about 1,500 calories.

"The predominant role in changing the microbiome of these children is done by the diet," Lionetti said. "We change our flora depending on what we eat."

He and colleagues concluded that the data indicate the importance of "preserving this treasure of microbial diversity from ancient rural communities worldwide."

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